miniprogramme/utils/image-cache-manager.js

/**
 * 图片缓存管理器
 * 实现头像和聊天图片的缓存功能
 */

class ImageCacheManager {
  constructor() {
    this.cache = new Map();
    this.cacheExpiry = new Map();
    this.maxCacheSize = 100; // 最大缓存数量
    this.cacheExpiryTime = 7 * 24 * 60 * 60 * 1000; // 7天缓存过期时间
    this.avatarCacheExpiryTime = 30 * 24 * 60 * 60 * 1000; // 头像30天缓存过期时间
    
    // 初始化缓存
    this.initCache();
  }

  /**
   * 初始化缓存，从本地存储加载
   */
  initCache() {
    try {
      const cachedData = wx.getStorageSync('image_cache');
      if (cachedData) {
        const data = JSON.parse(cachedData);
        this.cache = new Map(data.cache || []);
        this.cacheExpiry = new Map(data.expiry || []);
        console.log('📦 图片缓存初始化完成，缓存数量:', this.cache.size);
      }
    } catch (error) {
      console.error('❌ 初始化图片缓存失败:', error);
    }
  }

  /**
   * 保存缓存到本地存储
   */
  saveCache() {
    try {
      const data = {
        cache: Array.from(this.cache.entries()),
        expiry: Array.from(this.cacheExpiry.entries())
      };
      wx.setStorageSync('image_cache', JSON.stringify(data));
    } catch (error) {
      console.error('❌ 保存图片缓存失败:', error);
    }
  }

  /**
   * 清理过期缓存
   */
  cleanExpiredCache() {
    const now = Date.now();
    const expiredKeys = [];

    for (const [key, expiryTime] of this.cacheExpiry.entries()) {
      if (now > expiryTime) {
        expiredKeys.push(key);
      }
    }

    expiredKeys.forEach(key => {
      this.cache.delete(key);
      this.cacheExpiry.delete(key);
    });

    if (expiredKeys.length > 0) {
      console.log('🧹 清理过期缓存:', expiredKeys.length, '个');
      this.saveCache();
    }
  }

  /**
   * 清理超出最大数量的缓存
   */
  cleanExcessCache() {
    if (this.cache.size <= this.maxCacheSize) return;

    // 按过期时间排序，删除最旧的
    const sortedEntries = Array.from(this.cacheExpiry.entries())
      .sort((a, b) => a[1] - b[1]);

    const excessCount = this.cache.size - this.maxCacheSize;
    const keysToDelete = sortedEntries.slice(0, excessCount).map(([key]) => key);

    keysToDelete.forEach(key => {
      this.cache.delete(key);
      this.cacheExpiry.delete(key);
    });

    console.log('🧹 清理超出限制的缓存:', keysToDelete.length, '个');
    this.saveCache();
  }

  /**
   * 生成缓存键
   */
  generateCacheKey(url, type = 'image') {
    return `${type}_${url}`;
  }

  /**
   * 检查缓存是否存在且有效
   */
  isCached(url, type = 'image') {
    const key = this.generateCacheKey(url, type);
    const expiryTime = this.cacheExpiry.get(key);
    
    if (!expiryTime) return false;
    
    if (Date.now() > expiryTime) {
      // 缓存已过期，删除
      this.cache.delete(key);
      this.cacheExpiry.delete(key);
      return false;
    }
    
    return this.cache.has(key);
  }

  /**
   * 获取缓存的图片路径
   */
  getCachedPath(url, type = 'image') {
    const key = this.generateCacheKey(url, type);
    return this.cache.get(key);
  }

  /**
   * 缓存图片
   */
  async cacheImage(url, type = 'image') {
    if (!url || url.startsWith('data:') || url.startsWith('/')) {
      return url; // 不缓存base64、本地路径等
    }

    const key = this.generateCacheKey(url, type);
    
    // 检查是否已缓存
    if (this.isCached(url, type)) {
      console.log('📦 使用缓存图片:', url);
      return this.getCachedPath(url, type);
    }

    try {
      console.log('📥 开始缓存图片:', url);
      
      // 下载图片
      const downloadResult = await new Promise((resolve, reject) => {
        wx.downloadFile({
          url: url,
          success: resolve,
          fail: reject
        });
      });

      if (downloadResult.statusCode === 200) {
        const localPath = downloadResult.tempFilePath;
        
        // 设置缓存过期时间
        const expiryTime = type === 'avatar' 
          ? Date.now() + this.avatarCacheExpiryTime 
          : Date.now() + this.cacheExpiryTime;

        // 保存到缓存
        this.cache.set(key, localPath);
        this.cacheExpiry.set(key, expiryTime);

        // 清理过期和超量缓存
        this.cleanExpiredCache();
        this.cleanExcessCache();

        console.log('✅ 图片缓存成功:', url, '->', localPath);
        return localPath;
      } else {
        console.warn('⚠️ 图片下载失败，状态码:', downloadResult.statusCode);
        return url;
      }
    } catch (error) {
      console.error('❌ 缓存图片失败:', url, error);
      return url;
    }
  }

  /**
   * 缓存头像
   */
  async cacheAvatar(url) {
    return this.cacheImage(url, 'avatar');
  }

  /**
   * 更新头像缓存（当头像URL变化时）
   */
  async updateAvatarCache(oldUrl, newUrl) {
    if (oldUrl && oldUrl !== newUrl) {
      const oldKey = this.generateCacheKey(oldUrl, 'avatar');
      this.cache.delete(oldKey);
      this.cacheExpiry.delete(oldKey);
      console.log('🔄 更新头像缓存:', oldUrl, '->', newUrl);
    }
    
    if (newUrl) {
      return await this.cacheAvatar(newUrl);
    }
    
    return newUrl;
  }

  /**
   * 预加载图片（用于聊天中的图片）
   */
  async preloadImage(url) {
    return this.cacheImage(url, 'chat_image');
  }

  /**
   * 获取缓存统计信息
   */
  getCacheStats() {
    const now = Date.now();
    let avatarCount = 0;
    let imageCount = 0;
    let expiredCount = 0;

    for (const [key, expiryTime] of this.cacheExpiry.entries()) {
      if (key.startsWith('avatar_')) {
        avatarCount++;
      } else if (key.startsWith('image_') || key.startsWith('chat_image_')) {
        imageCount++;
      }
      
      if (now > expiryTime) {
        expiredCount++;
      }
    }

    return {
      total: this.cache.size,
      avatar: avatarCount,
      image: imageCount,
      expired: expiredCount,
      maxSize: this.maxCacheSize
    };
  }

  /**
   * 清空所有缓存
   */
  clearAllCache() {
    this.cache.clear();
    this.cacheExpiry.clear();
    this.saveCache();
    console.log('🗑️ 清空所有图片缓存');
  }

  /**
   * 清理指定类型的缓存
   */
  clearCacheByType(type) {
    const keysToDelete = [];
    
    for (const key of this.cache.keys()) {
      if (key.startsWith(`${type}_`)) {
        keysToDelete.push(key);
      }
    }

    keysToDelete.forEach(key => {
      this.cache.delete(key);
      this.cacheExpiry.delete(key);
    });

    console.log(`🗑️ 清理${type}类型缓存:`, keysToDelete.length, '个');
    this.saveCache();
  }
}

// 创建单例实例
const imageCacheManager = new ImageCacheManager();

module.exports = imageCacheManager;